Handout file picture released by Cuban website www.cubadebate.cu of Fidel Castro during the presentation of the two volumes of his new book, "Guerrillero del tiempo (Time Guerrilla)," on February 3 in Havana.

By NBC News staff and wire reports

Amid rumors that Fidel Castro's health had deteriorated, a message from the Cuban revolutionary leader was read out on his behalf at an event in Havana on Wednesday.

In a news item broadcast on state television, Cuba’s Minister of Public Health Roberto Morales was seen and heard delivering the statement marking the 50th anniversary of a Havana medical school, according to AP Television.

In it, the former president paid tribute to the thousands of clinicians who had graduated from the institute over the past half-century and reminded those present why it had been set up.

"The institute was inaugurated in response to the criminal action by the neighboring empire (referring to U.S.) to take, as it did with promises of visas and employment, the majority of our 6,000 medical doctors in this country," said Morales, reading the statement from Castro.

The health and location of Fidel are shrouded in mystery. The Associated Press reported that Castro had been mostly out of sight since he left office in 2006 due to a life-threatening intestinal condition. At times the only word on how he was doing came in remarks from ally Hugo Chavez, Venezuela's president. On October 4, Chavez told reporters Castro had been in touch to comment on Venezuela’s presidential campaign.

NBC News' Peter Jeary and The Associated Press contributed to this report.